Published October 2009
Bayer has recently developed a new phosgenation technology to produce toluene diisocyanate (TDI). The process is based on a gas-phase reaction that requires much less solvent and shorter residence time than the conventional liquid-phase process. This results in larger maximum capacities in a single TDI production train and lower investment costs for a plant of given size. Bayer has installed a pilot plant in its Dormagen, Germany, facility using this technology, and will commercialize it in the new 300,000 t/yr plant being built in Caojing, China.
In this review, we present a conceptual design and preliminary economics for an integrated plant producing 300,000 t/yr of TDI from toluene via DNT and TDA, using the gas-phase technology for the phosgenation step.
We also compare the economics of phosgenation using the gas-phase and the conventional liquid-phase processes. Our analysis indicates that the gas-phase technology offers a significant economic advantage over the conventional phosgenation process. In addition, the possibility of building an integrated TDI plant of 300,000 t/yr in a single production train leads to substantial economies of scale. Further benefits of the new technology include improvements in process safety by the reduction in phosgene inventories and the ability to start up and shut down the plant fairly quickly.